The present invention relates to a water treatment method using a hollow fiber membrane and an apparatus therefor, and particularly, to a direct-suction type water treatment method using a hollow fiber membrane and an apparatus therefor, in which a direct-suction filtration method is used to enhance the water treatment efficiency, and pollutants attached to the hollow fiber membrane are removed by a direction-convertible stirrer in a water tank containing the hollow fiber membrane to thereby extend the life of the membrane.
A hollow fiber membrane is of a thread from which has a hole in the middle thereof as in a straw and has fine holes on the surface thereof. Such a hollow fiber membrane is used for obtaining filtrate in which pollutants are removed in a water treatment system. In a water treatment system using a hollow fiber membrane, enhancement of the water treatment efficiency according to the treatment capacity, and extension of the life of the hollow fiber membrane in use are recognized as crucial points for determining the performance of the water treatment system.
Prior to describing the water treatment method using a hollow fiber membrane and an apparatus therefor according to the present invention, the conventional water treatment methods using the hollow fiber membrane will be described below.
There are a dead-end filtration method and a cross-flow filtration method as conventional water treatment methods using hollow fiber membranes.
FIG. 1 is a view showing a conventional water treatment apparatus employing a dead-end filtration method. In the water treatment using the dead-end filtration method, the influent water is passed through a hollow fiber membrane housing 10 and pollutants among the influent water are filtered by a hollow fiber membrane 11 as follows.
The influent water is introduced into the membrane housing 10 via an influent water solenoid valve 15 which is controlled by an electric signal from an original water tank 12 by the power of an influent water pump 14. The filtrate in which pollutants are removed by the hollow fiber membrane 11 are collected into a filtrate water tank 13 by a filtrate water solenoid valve 16.
The above-described water treatment method using the dead-end filtration method performs an air scrubbing or a back-washing using the filtrate water, to remove the pollutants accumulated in the hollow fiber membrane housing 10.
The air scrubbing method introduces the air discharged from an air compressor into the hollow fiber membrane 10 via an air scrubbing solenoid valve 19, while the back-washing method introduces the filtrate, in which pollutants are already removed, into the hollow fiber membrane 10 by a back-washing pump 18, to thereby clean the pollutants attached to the hollow fiber membrane 11.
The pollutants which are removed from the hollow fiber membrane 11 by the cleaning process and accumulated in the hollow fiber membrane housing 10 are discharged by a drain solenoid valve 17 to the outside.
However, the above cleaning process makes the water treatment apparatus complicated. Also, in the above cleaning process, the water treatment method according to the dead-end filtration method quickly increases the quantity of the pollutants accumulated in the hollow fiber membrane to thereby block the hollow fiber membrane causing the life of the hollow fiber membrane to be shortened.
Another conventional water treatment method employing the cross flow filtration method solves the defect of the hollow fiber membrane pores being blocked by the pollutants in the water treatment using the dead-end filtration method. FIG. 2 is a view showing a water treatment apparatus employing a cross flow filtration method.
The cross flow filtration method continues to circulate the water via a circulation solenoid valve 29 to thereby prevent the pollutants from being accumulated in the hollow fiber membrane housing 20. An influent water pump 24, an influent solenoid valve 25, a filtrate solenoid valve 26, a drain electronic valve 27 and a back-washing pump 28 in the cross-flow filtration method are the same as those in the dead-end filtration method in terms of their functions thereof.
As the flow speed of the circulation water increases, the cross flow filtration method reduces the tendency of accumulation of the pollutants in the hollow fiber membrane compared with the dead-end filtration method, resulting in the extension of the life of the hollow fiber membrane. However, to keep the speed of the circulated water flow, much more amount of water should be circulated than the amount of water to be treated by the water treatment apparatus, which causes much energy consumption.